Rich Stadnik of Greenfield tromps through the grass at the edge of the road at Greenfield State Park. The long grass, branches and tangled vines on the ground don’t stop him. He just makes his way steadily to a little grouping of apple trees that a less-trained eye might miss, tucked away as they are. The apples on the tree are small yet and immature, with no fruit falling to the ground to indicate they’re ready to be picked. He plucks one anyway, slicing it in half to examine the color of the seeds.

“This is how you discover apples,” he says conversationally. “You just march through the property and you look at an apple tree.”

At another tree, he might have also pulled out his refractometer to determine the sugar content of its apples. That’s one of his main criteria for a good apple, Stadnik noted, because a high sugar content means an apple has the potential to be good for cider, and that’s Stadnik’s business.

But Stadnik doesn’t have to test the apples on this tree and not only because they’re not ripe yet. This tree and its variety of apples is well-known to Stadnik. It’s called “Pup’s 07B2,” after Stadnik’s hard cider business, Pup’s Cider Company, which is based in Greenfield. “It’s a really romantic name,” joked Stadnik. These trees are among a long list of stand-alone and forgotten apple trees around the region Stadnik has found, left to grow there by farmers who planted them or grown from the seeds of discarded apple cores or from manure from horses or cows that have been eating apples. But it’s likely there are many he hasn’t found, hidden in roadside brush or in back fields.

When Lenny Cornwell, the president of Greenfield’s Historical Society, asked Stadnik to give a talk at the Greenfield Historical Society Museum this month, Stadnik decided to make it about the local wild apple population or, as he refers to them, the region’s “feral” apples. He’ll be showing attendees the characteristics to look for in a good apple, and how to tell if they’re ripe, when they’ll be at the highest sugar content and the sweetest.

First, look at the tree itself, he advises. Many feral apple trees are duds that don’t supply tasty fruit, but others were cultivated by farmers who no longer work the land and have left the trees to themselves, which usually means better fruit, according to Stadnik. The ones near former homesteads, that are spaced widely apart but in the same area and have different characteristics from each other, were planted deliberately, and may have once been a popular regional favorite. Ones on the sides of the road, halfway in the woods, are more likely to have once been an apple core thrown from a car window, he says.

“It’s a little bit of hypothetical and detective work, and a lot of imagination,” said Stadnik . “You just have to use educated guesswork to come up with a likely provenance of the apple, and you might be completely wrong.”

Stadnik has been in the business of discovering feral apples since the late 1990s, when he became interested in the process of grafting, or using cuttings from one tree and attaching it to rootstock to grow a new tree. He was involved in the software business at the time and wanted something completely different, he said in an interview Wednesday. “I had no experience with grafting plants, but I’ve always enjoyed apples. And I’ve lived in the Northeast my entire life, and there’s lots of varieties here. It gets me away from my computer and outdoors, and lot of good things like that.”

Apples are a good choice for grafting because they are so varied that they don’t often grow true from seed, said Stadnik. They are so cross-pollinated that seeds from the same apple can create fruit with different characteristics, he said. His new hobby led to a business creating hard cider from local fruit, both those he grows himself and from other local farms. Now, he’s constantly on the lookout for apples that will give new flavor to Pup’s Cider. Cider tastes best when it uses a blend of apples, he said. Pup’s Cider also partners with independent growers, vintners and distillers to import ciders, wines and specialties into the U.S.

“I’m not looking for the next great find,” said Stadnik. “I’m looking at the sugars, and asking, ‘Does it contribute anything to cider?’”

While Stadnik is seeking good cider apples, there are occasional other gems he stumbles across that have the potential to be market apples. When he finds those, he sends along his carefully recorded information about the location and characteristics of the tree to Cornell University, which houses a database of different varieties of apples. Usually though, the trees he finds are for his own personal collection. He tests the apples in the fall, and the ones that are promising for cider, he returns to in February or March to take cuttings.

Stadnik will be speaking on the importance of feral apples at the Greenfield Historical Society on Sept. 18 at 7 p.m. The event is free. Residents may bring in feral apples to test their sugar content.